The schematic above illustrates the key elements of an effective earthing system.
|
An effective earthing system is a fundamental requirement of any modern
structure or system for operational and/or safety reasons. Without such
a system, the safety of a structure, the equipment contained within it
and its occupants is compromised.
Earthing systems typically fall into (but are not limited to) one of the following categories:
 Power generation, transmission and distribution
Lightning protection
Control of undesirable static electricity
Telecommunications.
|
Conductors and Earth Rods
As
with lightning protection, the first choice faced by the designer of an
earthing system is the type of conductor to be used. The correct choice
of conductor is extremely important, whether it be a simple below
ground electrode or a complex computer room signal reference grid.
|
Conductors
Furse offer three types of conductor: Flat tape Solid circular and Stranded cable.
A
range of conductor materials are available. Above ground, copper,
aluminium and steel may be used. Below ground, copper is the most
common choice due to its high resistance to corrosion.
It
is important that earthing conductors should be correctly sized for
their application, as they may be required to carry a considerable
current for several seconds. For specific information on conductor
ratings see Conductor Ratings.
|
|
Earth Rods and Plates
In
addition to the conductors outlined above, earth rods and plates or any
combination thereof can be used to achieve an effective earth depending
on the site conditions.
Earth rods take advantage of lower resistivity soils at greater depths than normal excavation will allow.
Earth
plates are used to attain an effective earth in shallow soils with
underlying rocks or in locations with large amounts of buried services.
They can also provide protection at potentially dangerous places eg HV
switching positions.
|
|
Connectors and Terminations
An effective earthing system relies on joints and connections to have
good electrical conductivity with high mechanical strength. Poorly
chosen or badly installed joints and connectors can compromise the safe
operation of an earthing system.
Furse offer a range of connectors and termination methods to suit a wide range of applications.
|
|
FurseWELD Exothermic Welding
A
simple, self-contained method of forming high quality electrical
connections which requires no external power or heat source.
Connections are made using the high temperature reaction of powdered
copper oxide and aluminium.
FurseWELD
connections allow conductors to carry higher currents than other types
of connections. They will never loosen, are highly conductive and have
excellent corrosion resistance.
|
|
|
Compression Connectors
For
applications where exothermic welding is not appropriate for creating
permanent connections, compression connectors may be used.
Compression connectors produce very robust joints which can be buried in the ground or in concrete.
|
|
Mechanical Clamps
Where
permanent connections are not appropriate, mechanical clamps offer the
ideal solution. These are typically used on smaller scale installations
where periodic disconnection for testing is required.
All
Furse mechanical clamps are manufactured from high copper content
alloy. They have high mechanical strength, excellent corrosion
resistance and conductivity.
|
|
Earth Inspection Pits
Regular
inspection and testing of the earthing system is essential. Inspection
pits allow easy access to earth electrodes and conductors to facilitate
this procedure.
|
|
Earth Bars
Earth
bars are an efficient and convenient way of providing a common earth
point. Integral disconnecting links mean the earth bars can be isolated
for testing purposes.
|
|
Soil Conditioning Agents
Soil
conditioning agents are to be used in areas where required resistivity
levels are difficult to achieve. When used as a backfill for earth
electrodes, soil conditioning agents effectively act to increase the
electrodes surface area thus lowering its resistance to earth.
|
|
This illustration is designed to demonstrate the main aspects and
individual components of an earthing system. It is not intended to
represent an actual scheme conforming to a particular code of practice.
The drawing is not to scale.
|
| Earthing Lightning Protection |
| Earth Rods | Accessories | Static earthing kits | Compression connectors | Compression Tools |
| Earthing design considerations |
|
